A technique related to the fuel tank described above is disclosed in JP-A-2008-168767.
As illustrated in FIG. 8, a fuel tank body 100 of the fuel tank is configured by joining an upper shell 101 and a lower shell (illustration is omitted). A container body 122 of a canister 120 is molded integrally with the inner side of the upper shell 101 at the ceiling portion. In the container body 122 of the canister 120, an atmosphere port 120a and a purge port 120p are formed at positions of the ceiling portion of the upper shell 101, and an opening portion 122h is formed at the lower end position of the container body 122. In addition, the opening portion 122h of the container body 122 is configured to be closed by a cover material 124. A partition 122w that protrudes downward is formed at the ceiling portion of the container body 122, and the atmosphere port 120a and the purge port 120p are separated by the partition 122w to the left and the right. In addition, a vertical wall 124w that protrudes upward and is disposed parallel to the partition 122w of the container body 122 is provided in a cover material 124, and on the lower surface side of the cover material 124 positioned on the right of the vertical wall 124w, a tank port 120t including a bidirectional check valve is provided. That is, the inside of the container of the canister 120 is partitioned by the partition 122w and the vertical wall 124w and has a passage T formed to reach the purge port 120p and the tank port 120t from the atmosphere port 120a. In addition, the inside of the passage T of the canister 120 is filled with an adsorbent C to which fuel vapor is adsorbed.
During a stop of an engine, when the pressure in the fuel tank body 100 is increased due to a temperature rise or the like, air and the fuel vapor in the fuel tank body 100 flow into the canister 120 via a cut-off valve 111, a vapor passage 112, and the bidirectional check valve of the tank port 120t. In addition, the fuel vapor that flows in from the tank port 120t is adsorbed to the adsorbent C such that only the air diffuses to the outside from the atmosphere port 120a. 
In addition, during driving of the engine, a negative pressure is applied to the purge port 120p that communicates with an intake passage (illustration is omitted) of the engine, air flows into the canister 120 from the atmosphere port 120a, the air flows in the passage T to cause the adsorbent C to be subjected to a purge, and thus the fuel vapor is desorbed from the adsorbent C. In addition, the fuel vapor desorbed from the adsorbent C and the air are supplied to the intake passage of the engine from the purge port 120p. 
JP-A-2008-168767